The present invention relates to a mandrel rod holding device, particularly for continuous rolling mills for the manufacture of seamless pipes by means of rolling in several driven rolling stand, the rolling to occur onto an elongated mandrel which is retarded in a controlled manner during stretching the hollow by means of a mandrel shifting block being releasably connected to the end of the mandrel rod and being movable in the direction of rolling by means of a drive; the mandrel rod is released after the trailing end of the pipe has passed one or several of the stands and will continue to run through the rolling mill in the direction of rolling.
The manufacture of seamless pipes in a continuous rolling mill and in accordance with the method described above is condition on the fact that the mandrel rod with the mandrel is retarded relative to the pipe, at least during a portion of the rolling process. This way it is made possible that the heat resulting from friction work of the mandrel surface is reduced, as compared with a known method, on account of a considerably reduced relative speed between mandrel and pipe. Due to the fact that during the propagation of the front end of the hollow through the first stand the speed of propagation of the mandrel is lower than its working speed, one obtains, however, a relatively large retarding and holding force in the mandrel rod which has to be taken up by the mandrel shifting block.
The known method provides for an increase in through put and for avoiding delays during the retraction of the mandrel rod, in that the mandrel be released after the trailing end of the hollow has entered one of the first frames, i.e., the mandrel is no longer to be held. The mandrel and the mandrel rod will leave the mill in the direction of rolling.